While watching an episode of TNG I heard Data state that he was 'several times stronger than a human', which got me to thinking how much stronger than an average human is an average Klingon?
As a species? Possibly not at all, but it's sort of impossible to say. We're never given an objective, in-universe statement on the subject, assuming such a comparison is even really possible. 95% of all Klingons we ever meet are in the Klingon Defense Force (just as 95% of all Humans we see are in Starfleet).
However, we do know that members of the Klingon Defense Force train continually in hand-to-hand combat. This is partially just a cultural thing -- Klingons, or so we're told, just like to fight (which seems also overly general, but we never see enough Klingon civilian life to refute it); but it's also a reflection of the KDF's focus on being a true military force. Klingon doctrine still focuses in part on boarding actions (DS9: "The Way of the Warrior") and thus, Klingon crews need to be able to fight in close quarters with edged weapons and simple muscle power, as well as hand-held disruptors. Worf, seeking to be as Klingon as he can while living amongst humans, emulates this to the point where he's at least a match, one-on-one, with most Klingons and, as we eventually see, many Jem'Hadar, who also train continually for hand-to-hand combat.
By contrast, while Starfleet presumably values health and fitness, they do not see themselves as a primarily military organization, and are not all that keen on boarding actions when forced to flight. They're not interested in taking prizes for their own sake, and so, at least in what we've seen on-screen, are more likely to board a disabled vessel to provide medical assistance than to attempt to neutralize its crew and capture it! In short, we see no evidence that Starfleet crews continually train for hand-to-hand combat the same way.
In the end, though, in terms of on screen evidence, I can only think of three situations in which there is any sort of melee action between multiple humans and multiple Klingons:
- The bar-room brawl in TOS: "The Trouble With Tribbles" (and DS9: "Trials and Tribblatons")
- The ongoing fighting in TOS: "Day of the Dove"
- The Klingon attempt to take DS9 in DS9: "The Way of the Warrior"
In each case, we ultimately see that the humans involved actually hold their own against their Klingon opponents, despite the differences in their training. In "The Way of the Warrior", the boarding action is ultimately neutralized, in fact, by the predominantly human and Bajoran station personnel, despite the fact that it does come down to hand-to-hand combat at close quarters.
Just as a few people have already pointed out. Humans, like Klingons, differ greatly in size and strength even within their own race. And like any other race you have larger and stronger members of the race.
Which brings us to Worf. Simply put, Worf is a big, strong Klingon. You see this when he is near other Klingons and when he fighters others. But when taken as a race in general? I would actually make a argument that Klingon's are on average slightly weaker then humans. But built more durably.
TOS should also be considered slightly ... separately than TNG. Simply put, Klingons underwent a change in canon between the two (beginning in the movies). I think Klingons were actually meant to be treated as physically more impressive in TNG/Movies. Also slightly less ... shall we say greasy ... That's not a joke on the make up. Klingon's where really framed as a less cunning more warrior/brute culture in TNG than in TOS.
In TOS they were underhanded and petty to a much larger extent. The argument of "honor" was really a very backhanded matter of simple respect, not actually being fair/just (which honor has nothing to do with, anyway).
We see time and again that Star Fleet Personnel hold their own against Klingon warriors. And there is a great comparison to this: The Marines and the Navy. Star Fleet is the Navy. A more technically-based, physically-fit -- but not 'warrior' -- culture group. The Klingons are the Marines -- a warrior culture.
And you bet your buns that the Marines are as a group in better actual shape then the Navy. But physical shape only goes so far.
A simple example. I'm 5'3" and Weighed 175lbs when I was in the Army. (I'm a short stocky guy). My best friend was in the Marines at the same time, he's 6'0" and weighed about 160lbs at the same time. He was in WAY better shape than me. Much better PT scores. Much much better running time. On a mat / boxing ring I would run him out of the ring. The simple reason is that I am physically stronger. (Also, we are talking 15 years of martial arts vs Marine hand-to-hand). Compare both of us to my older brother, who is 5'10" and 270lbs, but looks like he is 200, tops. He's simply built of something like dark matter. And he could literally flatten both of us at the same time.
Yes, being in shape helps. But actual natural psychical ability matters a lot. If the Klingons were as strong as humans (not even stronger), they should be rolling humans over when they fight them.
I have a actual biological explication for this: redundancy. As we know, Klingons have redundant EVERYTHING -- spines, organs, bones -- and all of that is soft/hard tissue -- not MUSCLE. On average, a human male is about 15% bone, 45% muscle, 25% organs, 15% fat. The simple explanation for the Klingon strength issue is that more of that weight is bone/organs. A 200lbs human man will have 90lbs of muscle. A 200lbs Klingon man might have 80lbs? 70lbs? of muscle.
So, even if Klingons are on average a little bit heavier than humans (although there is no real indication of this), they would have about the same muscle mass or less.
Examples. Day of the dove: The crew from the Enterprise (Mind you NOT the security team) Is holding there own against Klingon Warriors. The rank and file crew members of the Enterprise are mostly scientists and engenders. The Klingon (So we are told) are warriors. All of them skilled in hand to hand and melee fighting. So there the part about being skilled in hand to hand and melee is a total lie and Klingon are as strong as humans. Or Klingon are stronger and are worse at hand to hand then the average crew member. - Or they are better at hand to hand and weaker. - They can't be both more skilled and stronger and be 'holding there own.'
It would be like some one saying "I have a 5th degree black belt in Karate." and then holding there own to some Navy Mechanic who has only had PT and basic hand to hand. Ether that Mechanic is in MUCH better shape. Is natural stronger. Or that black belt's black belt isn't worth anything... or he's lying.
Considering that Worf has shown Klingon martial arts to be pretty good. That does not seam to be the case.
First Battle of Deep Space 9. The klingon's (Armed with Melee weapons) where beaten back by the Crew of DS9. Yes some of them where actually security forces. But that's the issue. If the Security forces are skilled fighters that should put them on par with the klingon's ONLY if they are the same strength. - A lot of the crew where not security.
Let's also talk about Worf/kira. As we have pointed out Worf is a monster of a Klingon and very skilled at hand to hand. So it makes sense he is handling three Klingons.
Kira on the other hand is (More or less cannon) very skilled but not quite as much as Worf. And is not nearly as strong... She takes out three Klingons at once and then gets stabbed.
So again, ether the rank and file Klingon warrior is actually abjectly terrible at hand to hand and its just bluster. Or there warriors are about as strong as a the average star fleet personnel.
Riker So I can except that A:Riker is a big human and in good shape. B:Riker is a damn good fighter. But he still did pretty well in a fight against a Klingon First office.
Klingon weight/muscle mass.
I made this point and some one asked for example. Well I don't actually need a example. I clearly explained that this was a Ideal. And gave my reasoning. Klingon have a lot of extra bones. And organs. (The organs might be smaller mind you, and just more of them) But still that would support the ideal that a human that was the same weight as a Klingon would have more muscle mass. And less bone mass.
The point is not that Klingons MUST be weaker then Humans. It's that if they are not something else is massively leveling the playing field for the Federation. So let's consider a few other options.
#1: All star fleet personnel are literally Martial arts experts.. Which is unlikely. While they all take hand to hand in the Academy. (Don't know about enlisted) It's clearly not up to the level of even what (Black belts, which is a kind of meh way to measure in real life) get. - To the point that the show actually notes in TNG that one of the crew members is a 3rd Degree black belt in TKD.
It's much more likely that the Federation crew members are about as well trained as US military personnel. Which means ranging from "A few days of training in Basic." All the way up to Expert or comparative to a serious part time practitioner. (Because unlike most people think, pretty much no one in the military is a super bad ass in hand to hand BECAUSE they are in the military, they are because its there past time) You don't see any MMA guys from the army do you? That's because hand to hand is simply not that important, even Special forces hand to hand is more about killing some one with the element of surprise quickly and quietly.
#2: Humans are apparently near super human in the future? This is actually something that has been talked about. So before I start I need to make a point.
This would still not make sense COMPARATIVE TO KLINGON. If humans in star trek are twice as strong (Example) As modern humans. It still would be comparing Star Trek Humans to Klingons.
But. Point 1: There are no short humans in star trek.... Really.. The Shortest crew member we see in Star Fleet is Janeway. Who's 5'5" Which is a little short for a women but not that short. (I for instance am 5'4" as a man) - Geordi is not much taller then Janeway. But still not that short. Just a little below average. - This makes sense, there would be pretty much no such thing as a malnourished human in Star Fleet. - Actually humans in general would have Exactly the dietary intake they needed growing up.
Point 2: There are not overweight humans in star fleet.... Even farther then the modern military. Every one in star trek is filling out those uniforms pretty well. Again this makes sense, its very likely there is a hypo spray that makes you burn fat. And Again diet is perfect.
Point 3: No actual injuries for the most part. Break you shoulder? It will be literally good as new in a few days.
Now for the Klingons.
#1: Klingon Warriors are actually in no better shape then Klingon Civilians. It IS possible that we are seeing literally the best that humans have to offer (Star Fleet) Being pitted against space garbage Klingon. That Klingon warriors are lazy slobs or there civilians are super hard working and are thus always in great shape.
But that still brings us to the problem that If Klingons are better fighters then Humans. And stronger why are they not winning more. Well, this might support that Klingon's are about as strong as a human.
#2: The entire ideal that Klingon warriors are good at hand to hand or Melee Combat is complete Gornpoop. There is also the possibility that Klingon are talking out there buts when it comes to the ideal that Klingon warriors are generally speaking really good at hand to hand and melee combat. And the small amount of training the average star fleet personnel gets puts them on the same level as Klingon warriors...
And I'm actually pretty sure there is something to this. I think the Klingon skill in hand to hand is vastly overstated. And that they are just more accustomed to hand to hand. But that should still be a advantage...
Simply put, there is no way that Klingons would not at least a slight advantage on average. I just don't think it's as big as the Klingons say it is.
#3: Klingons... are not as strong on average as humans. Now that would still mean that Klingon Warrior's (Who SHOULD Be stronger) would be about as strong as Star Fleet Personnel. But then what about NOT warrior Klingons? We are lead to believe that even Klingon Civilians are in good shape (Because of hard work) and are more accustomed to violence then Human Civilians.
And this would imply that Klingons just START on at a lower level then Humans.
So again. I make the argument that ether.
1: Klingons are actually garbage fighters. And only hold there own against Humans BECAUSE they are stronger.
2: Klingons are actually weaker then Humans and only hold there own because they are more skilled.
3: Some combination of the two.
4: Klingons are literally flinging the literally garbage of there race into space lead by a few really good leaders.
I am not sure about Klingons, but Vulcans, who seem also to be discussed in the answers and comments, are stronger because of the gravity of Vulcan. So Spock is much stronger than Kirk without appearing to be even as massive. Perhaps their muscle quality or whatever is superior. Similar arguments could be made about Klingon assuming conditions on Chronos are more harsh/demanding.